It is known to use a rotary can end lining machine in which the can sealing compound is dispensed on a turret arrangement to which there is a single feed of compound, and then distribution of the liquid compound to several lining stations around the periphery of the turret so that the compound can be dispensed while the turret is rotating and while the lining stations are orbiting around the axis of rotation of the turret.
For many years a turret has been used in which the can sealing compound is supplied in this way, but the compound has usually been a solvent-based compound in which rubber and resin are dissolved in a solvent and fillers are in suspension. Such a compound is not susceptible to the effects of shear.
The solvent would evaporate during drying, to leave a solid gasket. More recently, in order to avoid the emission due to evaporation of solvents, there has been a move towards water-based can sealing compounds and it has been found to be a disadvantage of such compounds that shear forces in the liquid, for example at any interface between stationary and rotating parts of the apparatus, give rise to coagulation of the compound which causes a build-up of the coagulated compound locally in the rotary union of the turret, and eventually interference with the flow of compound to the individual moulding stations.
There have been various attempts made in the past to avoid such a problem. For example, GB-A-2200059 uses a rotatable reservoir with flow into that reservoir vertically downwardly through a stationary dip tube on which are also mounted liquid level detectors to control the inlet of suspension into the reservoir within predetermined upper and lower limits. This will ensure that the interface between the suspension and the gas space thereabove remains well below the rotary seals between the stationary dip tube and the lid of the rotating reservoir. While such an arrangement does minimize the risk of contact of liquid with adjacent rotating and stationary surfaces of the apparatus at the seals, which occur well above the level of the reservoir around an upward extension of the dip tube, the fact that the reservoir is rotating around the stationary dip tube (for example at around 100 rpm) can present problems.